The present invention relates to a device for positioning a measuring element, for example, in the form of a doppler signal emitter and/or receiver for determining the position of a blood vessel and flow direction of the flowing blood wherein the measuring element is suspended by two parallelogram linkage systems that are arranged at an angle relative to one another such that the measuring element is movable in a random fashion about an adjustable point.
Such a device has been known from U.S. Pat. No. 4,817,621. The parallelogram linkage systems, with free ends thereof, are respectively pivotably supported at a reference plate whereby the parallelogram linkage systems are arranged relative to one another at a prescribed angle. When an examination is performed the parallelogram linkage systems are directly positioned at selected locations of the head of a patient. This device has been proven successful, however, the constructive expenditure is substantial, especially, because of the plurality of joints that are required. An economic manufacture is thus not possible and, furthermore, disruptions of the examinations do occur because the measuring element will not maintain its initial position. Furthermore, it is disadvantageous that the measuring element, since it is geometrically and mechanically fixed, may only perform pivoting movements about a fixed pivoting point. Also, examinations may only be performed when the patient is in a lying position so that not all locations of the head may be examined. Furthermore, the handling of the aforementioned device is difficult due to the substantial mass and weight of the device. A further restriction of the application of the aforementioned device is that a patient, during an examination, may not move his head because this may lead to incorrect results and requiring a correction of the position of the measuring element.
It is therefore an object of the present invention to provide a device for positioning a measuring element of the aforementioned kind which is of a simple construction and is thus economical to manufacture, and allows an uninterrupted operation. It is especially important that the measuring element may be aligned with certain location and may easily be positioned whereby the once attained position should be maintained during examination without having to correct the position so that examinations may be performed over an extended period of time. Furthermore, such examinations should be performable in any position of the patient, especially in a sitting position. It is also desirable that the device be mountable without difficulties on a holding device which is attached to the head of the patient so that movements of the head will not influence the position of the measuring element. A further object of the present invention is to provide the device such that planar and circular movements may be performed, that the pivoting point about which random movement occurs may be adjustable and that the movement of the measuring element may be programmable in a simple manner.